finalise interface & documentation

Signed-off-by: Folling <mail@folling.io>

src/id.hpp

@@ -0,0 +1,40 @@
+// IMPLEMENTATION_DETAIL_DATABASE
+
+/// \file id.h
+/// \author Folling <folling@ikarus.world>
+
+/// \privatesection
+
+#pragma once
+
+#include <ikarus/macros.h>
+#include <ikarus/objects/object_type.h>
+#include <ikarus/stdtypes.h>
+
+IKARUS_BEGIN_HEADER
+
+/// \defgroup id Ids
+/// \brief Ids are used to identify objects in the database.
+/// \details They are stored as 64 bit integers with the following layout:
+/// - first bit: ignored, technically we could use it, but SQLite doesn't support u64 integers.
+///   To avoid ordering fiascos and potential index performance degradation we just skip the first bit.
+/// - next 7 bits: #IkarusObjectType
+/// - last 56 bits: incremented counter generated by the database
+/// @{
+
+/// \brief A wrapper around a 64 bit integer that represents the id of an object.
+/// \details They are stored as 64 bit integers with the following layout:
+/// - first bit: ignored, technically we could use it, but SQLite doesn't support u64 integers.
+///   To avoid ordering fiascos and potential index performance degradation we just skip the first bit.
+/// - next 7 bits: #IkarusObjectType
+/// - last 56 bits: incremented counter generated by the database
+using IkarusId = int64_t;
+
+/// \brief Fetches the object type of the given id.
+/// \param id The id to fetch the object type for.
+/// \return The object type of the given id.
+IKA_API IkarusObjectType ikarus_id_get_object_type(IkarusId id);
+
+/// @}
+
+IKARUS_END_HEADER